Tardigrades, also known as water bears, can survive extreme conditions. For example, tardigrades have high tolerance to extreme desiccation because they can enter an anhydrobiotic state, in which they show no or nearly undetectable metabolic processes. Proteins from anhydrobiotic tardigrades with low homology to known proteins from other organisms are new potential targets for structural genomics. Here, we present spectroscopic and structural characterization of an unprecedented globin protein (Kumaglobin: Kgb) found in an anhydrobiotic tardigrade. Spectroscopy reveals that Kgb contains hexacoordinated low‐spin heme, which is not capable of binding to hydrogen sulfide (H2S) unlike other globin proteins, such as neuroglobin. Interestingly however, when distal histidine is replaced with alanine, H2S is capable of binding to heme, implying that the distal histidine of Kgb binds tightly to heme. The overall structure of Kgb at 1.5 Å resolution shows high resemblance to well‐characterized eukaryotic globin proteins, such as myoglobin and cytoglobin. However, the heme coordination geometry in Kgb is unique because the distal histidinyl ligand is located at the 11th position of helix E while it is found at 7th position on helix E in many known globin proteins. The unusual conformation of distal histidine in Kgb is stabilized by a hydrogen bond with the carbonyl O atom of A103. Furthermore, bulky residues exist around the heme cofactor, resulting in a ruffling conformation of the porphyrin ring. Based on our study, Kgb is thought to be involved in electron transfer or enzymatic reactions rather than transporting or storing ligands. Database Structural data are available in the Protein Data Bank under the accession numbers http://www.rcsb.org/pdb/search/structidSearch.do?structureId=5ZIQ (Kgb4‐SR) and http://www.rcsb.org/pdb/results/results.do?tabtoshow=Unreleased&qrid=D1773C9B (Kgb7‐house).

Cytochrome b 5 is an essential electron transfer protein, which is ubiquitously found in living systems and involved in wide variety of biological processes. Tardigrades (also known as water bears), some of which are famous for desiccation resistance, have many proteins unique to them. Here, we report spectroscopic and structural characterization of a cytochrome b 5 like protein from one of the desiccation‐tolerant tardigrades, Ramazzottius varieornatus strain YOKOZUNA‐1 ( Rv Cyt b 5 ). A 1.4 Å resolution crystal structure revealed that Rv Cyt b 5 is a new cytochrome b 5 protein specific to tardigrades.

Radioactive Cesium was released from nuclear accidents such as Fukushima and Chernobyl's nuclear power plant accident. The released cesium contaminated water and soil environment around the accident area. Common environmental technologies for water and soil could not be used for the cesium contaminated environment due to several reasons. The radioactive cesium exists as in a trace amount and with other common cations such as calcium and sodium. The co-exist cations interfere the removal of cesium and increase the final waste. Magnetic separation combined with adsorption technology can be applicable to the removal of radioactive cesium from water environments. In current study, a selective adsorbent for cesium, silicotitanate was synthesized and tested for cesium selectivity. The cesium selective adsorbent was magnetized and separated from water using a superconducting magnet. The decrease of sorption capacity was evaluated after magnetization. The cesium selectivity was sustained after the magnetization. The removal efficiency of magnetized silicotitanate was highly dependent on the magnetic field and magnetizing method. Complete removal of the magnetized adsorbent was achieved by a superconducting magnet indicating a superconducting magnet system with magnetized silicotitanate can be an alternative for water treatment from a nuclear accident sites. 

Tardigrades, a phylum of meiofaunal organisms, exhibit extraordinary tolerance to various environmental conditions, including extreme temperatures (−273 to 151°C) and exposure to ionizing radiation. Proteins from anhydrobiotic tardigrades with homology to known proteins from other organisms are new potential targets for structural genomics. Recently, we reported spectroscopic and structural characterization of a hexacoordinated haemoglobin (Kumaglobin [Kgb]) found in an anhydrobiotic tardigrade. In the absence of its exogenous ligand, Kgb displays hexacoordination with distal and proximal histidines. In this work, we analysed binding of the molecular oxygen ligand following reduction of haem in Kgb using a pulse radiolysis technique. Radiolytically generated hydrated electrons (eaq−) reduced the haem iron of Kgb within 20 µs. Subsequently, ferrous haem reacted with O2 to form a ferrous-dioxygen intermediate with a second-order rate constant of 3.0 × 106 M−1 s−1. The intermediate was rapidly (within 0.1 s) autooxidized to the ferric form. Redox potential measurements revealed an Eʹ0 of −400 mV (vs. standard hydrogen electrode) in the ferric/ferrous couple. Our results suggest that Kgb may serve as a physiological generator of O2▪− via redox signalling and/or electron transfer.

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